Conventionally, there has been known, as a vehicle display device, a head-up display device that superimposes and displays an information image from an image forming unit (image display) into a visual field of a driver (see, for example, PTL 1).
A display device disclosed in PTL 1 is configured to cause light generated by a display surface of an image forming unit to enter a windshield (window member) through a projection lens and guide the light from the display surface to a driver by causing the windshield to reflect the light. The display device disclosed in PTL 1 includes means for detecting a vibration state of a vehicle and a driving device that drives a projection lens, and changes a superimposition position of an image (virtual image) within a visual field of a driver by displacing the projection lens in accordance with a direction of vibration displacement. PTL 1 discloses a technique of reducing vibrations of a virtual image due to vibrations of a vehicle equipped with a display device.